Emergency Brake Assistant for Automatically Decelerating a Vehicle to Prevent a Collision or Reduce the Consequences of a Collision

ABSTRACT

The invention relates to an emergency brake assistant for automatically decelerating a vehicle to prevent a collision or reduce the consequences of a collision with a detected collision object, at a determined intervention point in time, a brake system of the vehicle being automatically activated such that a collision with the detected collision object can be prevented or at least the consequences of the collision can be reduced. The invention is characterized in that the intervention point in time can be determined as a function of the end point in time of a determined driver reaction time and of the determined last-possible braking point in time.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT International Application No.PCT/EP2011/051085, filed Jan. 26, 2011, which claims priority under 35U.S.C. §119 to German Patent Application No. 10 2010 006 214.6, filedJan. 29, 2010, the entire disclosures of which are herein expresslyincorporated by reference.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to an emergency brake assistant for automaticallydecelerating a vehicle to prevent a collision or reduce the consequencesof a collision according to the preamble of claim 1.

Modern driver assistance systems are capable of completely preventing animminent collision or at least minimizing the consequences of acollision by an autonomously initiated full brake application. By meansof a suitable sensor system (radar, lidar, image processing) or theevaluation of vehicle-to-vehicle communication, these systems detect thevehicle environment and determine possible collision objects. When acollision is imminent, a full deceleration will be initiated.

With an increasing relative speed between the given vehicle and thepotential collision partner, the path required for this braking will beincrease quadratically. Since, in comparison, the distance for a narrowovertaking maneuver or evading maneuver increases only in a linearfashion with the speed, at higher differential speeds, an overtaking orevading will still be possible after the point in time of acollision-preventing braking has already been exceeded. This so-calledintervention dilemma results in a target conflict for the design of theemergency brake assistant. If, when the last-possible braking point intime is reached, the assistant intervenes by means of a fulldeceleration, the collision will be prevented—a driver, who had planneda narrow overtaking or evading maneuver, will, however, be surprised bythe intervention. In order to prevent these decelerations subjectivelyperceived to be faulty and meet the product liability requirements, thesystems currently on the market are designed such that a braking doesnot take place before the point in time at which the driver can neitherby braking nor by overtaking or evading still autonomously prevent thecollision (“point of no return). However, at high differential speeds,this has the result that, also by means of the autonomous emergencybraking, the preventing of a collision is no longer possible—only theconsequences of the collision will be reduced.

From German Patent Document DE 601 26 398 T2, a brake control systemwith a system intervention in the event of an object recognition isknown, which, when the driver's intention to evade is recognized,suppresses an otherwise generated automatic braking intervention forpreventing a collision with a detected collision object.

It is an object of the invention to indicate an emergency brakeassistant which, while taking into account the above-mentioned problems,can determine an intervention point in time so that, on the one hand,the driver feels sufficiently safe and, on the other hand, is nothindered when carrying out his own driving action.

This object is achieved by means of a emergency brake assistantaccording to claim 1. Advantageous further developments are contained inthe dependent claims.

The invention is based on an emergency brake assistant for automaticallydecelerating a vehicle to prevent a collision or reduce the consequencesof a collision with a detected collision object, wherein, at adetermined intervention point in time, a brake system of the vehicle isautomatically triggered such that a collision with the detectedcollision object is prevented or the consequences of the collision areat least reduced.

In real road traffic, the driver will constantly experience events towhich he has to react in order to prevent a collision—these include thefollowing application cases relevant to an autonomous emergency braking:

-   -   A continuous approach to a vehicle ahead,    -   a sudden braking maneuver of a vehicle ahead as well as    -   an adjacent vehicle cutting into the given traffic lane.

Although no information concerning the subjective driver's perception isavailable, a model of these reaction triggers can be created by means ofthe vehicle sensor system. For this purpose, driving-psychologicalthreshold values are used which describe the transition from a followingto an approaching that requires a reaction.

Continuously approaching a vehicle within a given trajectory, which inmany situations takes place at a high relative speed, can also bedescribed independently of the distance by the time to collision (TTC).In the state of the art, a TTC value of 5 seconds is considered as athreshold below which the driver feels an acute need to act for againincreasing the gap between his vehicle and the other vehicle or forevading the obstacle by means of an overtaking maneuver.

In a limited differential speed range, this threshold value can also beindicated as a distance value. It is composed of a constant safetydistance when stopped as well as a speed-dependent value. By means ofthis minimal following distance, the cases of “sudden braking” and“cutting-in” can now be detected. If a vehicle driving ahead were todecelerate in traffic so much so that a following driver of a givenvehicle would fall below the safety distance while still moving, arequirement to act would arise for restoring the safe driving condition.This need to act also arises when a vehicle in the adjacent lane startsa cut-in maneuver within the minimal following distance.

Both events would also be recognizable by means of the time-relatedthreshold value TTC. However, the advantage of considering the distanceis exhibited by the example of a sudden braking. If the deceleration ofthe vehicle ahead starts in a driving condition in which it is stillmoving away from the given vehicle, the computation of the TTC would notyet be possible. By using the distance value, the starting point in timefor the beginning of the subsequent reaction can be identified also inthese cases.

The invention is characterized in that the intervention point in timecan be determined as a function of the end point in time of a determineddriver reaction time and of the determined last-possible braking pointin time.

The reaction time, which starts after the occurrence of thecorresponding reaction trigger and lasts until the point in time atwhich the driver reaction can be measured on the vehicle bus system, canbe modeled by means of the OODA activity sphere. This sphere representsthe individual components of human decision-making: O(bserve), O(rient),D(ecide), and A(ct).

The observation process as well as the activity process can be based onapproximately constant values averaged for all drivers. The duration ofthe mere perception of the situation is approximately 0.2 second; theexecution of the act—thus, the movement of the foot for the actuation ofthe pedal—because of frequent practice, takes approximately 0.3 seconds.

In contrast, the remaining process steps for the classification, as wellas for the decision-making, are dependent on the triggering event; i.e.,the driver's reaction time can be determined as a function of thecurrent vehicle environment and/or of the type of the occurrence of thecollision object. Unexpected triggers (for example, unpredictable strongbraking of the vehicle ahead) or events with a low probability ofoccurrence lead to a longer phase of decision-making than expected orfrequently occurring events. Together, these two process steps can bemodeled to be gamma-distributed.

In order to be able to derive a reaction time from the gammadistribution, the risk of exceeding a certain duration is considered.For this purpose, the cumulated gamma distribution is subtracted fromone. Accordingly, a risk of 20% means that, in the consideredexamination, 80% of the drivers required a shorter or precisely theresulting duration for the reaction to the triggering event.

In addition to the dependence on the triggering event or on the type ofthe occurrence of the collision object, the reaction time resulting fromthe OODA activity sphere will increase if several acting alternativesare available to the driver. Since the individual occurrenceprobabilities of the acting alternatives are unknown a priori, they areassumed to be evenly distributed.

For the application case of active danger braking, this means that, inaddition to the possibility of braking, the feasibility of an overtakingmaneuver also has to be examined. For this purpose, for example, thearea adjacent to the vehicle is, in each case, divided into threesub-areas: Behind the given vehicle, laterally at the level of the givenvehicle as well as in front of the given vehicle. For all areas, a valuerelevant to a lane change is computed and, in a comparison function, isstandardized to a factor between 0 (lane change not feasible) and 1(lane change safely feasible). The minimum of the three factorsdetermines the global lane change feasibility. If a defined thresholdvalue for the minimum is exceeded, it is assumed that a lane change intothe corresponding direction is feasible.

In the rear area, the necessary deceleration for an approaching vehiclein the event of a lane change of the given vehicle, is computed as avalue relevant to the lane change. In the front area, the necessarydeceleration for the given vehicle is analyzed should the latter carryout a lane change and the target lane already be occupied by anothervehicle. In the lateral area, the space required for making the lanechange is analyzed. The lane change feasibility is then obtained fromthe ratio between the necessary and the reasonable deceleration (rearand front area) or between the necessary and the available space in thelateral area.

Since, particularly when assuming that in the event of a detectedcollision object, the driver can possibly still overtake or evade, thelast-possible evading point in time has to be taken into account whendetermining the intervention point in time, this last-possible evadingpoint in time is also taken into account in an advantageous furtherdevelopment of the invention.

For determining the last-possible evading point in time or the necessarydistance for a narrow overtaking maneuver, for example, an overtakingparabola with an assumed lateral deceleration is placed in the free areabetween the given vehicle and the potential collision object. Thedistance in the longitudinal direction necessary for the overtaking orevading maneuver is then obtained as a function of the momentaryrelative speed, as well as the lateral distance to be overcome. Thelatter may consist of the widths of the given vehicle and the othervehicle/object as well as of the current object position. Since amaximal lateral acceleration cannot be assumed at low speeds, thelateral acceleration is adapted as a function of the speed.

Taking into account the end point in time of the determined driverreaction, a last-possible braking point in time determined (in a knownmanner) and the determined last-possible evading point in time, thesituation can be evaluated to the end of the reaction time, and therebyat least a preliminary intervention point in time can be determined foran autonomous braking intervention. For this purpose, as indicatedabove, the corresponding reaction time is first assigned to the threepossible reaction triggers. A continuous approach to a vehicle ahead is,in this case, considered to be an expected event; a sudden braking or acutting-in vehicle is considered to be an unexpected event. If, at thepoint in time of the occurrence of the reaction requirement, thecorresponding reaction duration is subtracted from the time to collision(TTC), the determined value—thus, the time after the reaction thatremains for preventing the collision—can be compared with the thresholdvalues for a braking or an overtaking or evading maneuver.

In the case of low differential speeds (i.e. here, with respect to thetime, the last-possible evading point in time is before thelast-possible braking point in time), the last-possible braking point intime can always be used as an intervention point in time, because thedriver has no other alternative for preventing the collision.

In the case of high differential speeds, at which an overtaking orevading is still possible after the last-possible braking point in time,however, three possible situations will occur.

If, with respect to the time, the determined end point in time of thedriver reaction time is before the determined last-possible brakingpoint in time, the last-possible braking point in time can therefore beselected as the preliminary intervention point in time because, in thecase of an autonomous collision avoidance by the driver, a correspondingreaction already exists beforehand. For this case, the avoidance of anaccident will therefore always be possible.

In the second case, it is assumed that the determined end point in timeof the driver reaction time occurs before the determined last-possibleevading point in time and after the determined last-possible brakingpoint in time. Since the probability of an autonomous mastering of thesituation by the driver is much higher than that of a rear collision, abraking intervention, if necessary, will be initiated only at the end ofthe reaction time. However, in the least favorable case, this may meanthat the emergency braking will no longer be sufficient for completelypreventing the collision. In order to partially solve this conflict, thestandardized value for judging the lane change possibility from thereaction time estimation will be used; i.e. in this case, thepreliminary intervention point in time is defined as a function of thefeasibility of an evading maneuver. In this case, the last-possiblebraking point in time is defined as the preliminary intervention pointin time if an evading maneuver is not feasible, while the determined endpoint in time of the driver reaction time will be defined as thepreliminary intervention point if an evading maneuver can be carried outsafely. If no lane change is possible, a fully collision-preventingbraking will therefore take place.

In the third case, it is assumed that the determined end point in timeof the driver reaction time is after the determined last-possiblebraking point in time and after the determined last-possible evadingpoint in time, the determined last-possible evading point in timeoccurring after the determined last-possible braking point in time. Inthis case, the automatic braking intervention may already be carried outat the last-possible braking point in time because a timely reaction bythe driver is very improbable.

For an even better definition of the intervention point in time of theemergency brake assistant, it is also important, in addition to theabove-mentioned parameters, to check and take into account the actualdriver reaction. In particular, the driver reaction (for example,braking or overtaking) occurring during and/or after the determineddriver reaction time should be taken into account. If there is areaction (or it is at least believed that there is a reaction) and it issufficient for the autonomous avoidance of the collision, or the evadingor take-over maneuver can be carried out, the preliminary interventionpoint in time determined in the differentiation of cases will be delayedto the so-called “point of no return”, thus the determined last-possibleevading point in time. Although the latter should never be reachedbecause of the driver reaction that was judged to be adequate, it cannevertheless be maintained as a fall-back level. Otherwise, thedetermined preliminary intervention point in time is defined as theintervention point in time.

Indicators can in each case be determined for the two action options“braking” and “overtaking”. A braking effect can be applied by thenormal operating of the brake pedal as well as by the buildup of dragtorque by releasing the gas pedal. The overtaking reaction can bedetected by recognizing a decreasing overlap with respect to the vehicleahead or by a corresponding course of the steering angle. For an earlyinclusion of the intention to overtake, the use of lane changemotivation models is obvious. The recognition of the flasher operationfor the lane change is a simplified approach for this purpose.

For checking whether the detected reaction is also present in a timelyand adequate manner, in the case of the braking, the applieddeceleration is compared with the deceleration required for preventingthe collision. The latter is a function of the momentary relative speedbetween the given vehicle and the collision object, the momentarydistance between the two vehicles as well as the deceleration of theother vehicle.

In the case of an existing intention or reaction for the purpose ofovertaking, it has to be checked—as mentioned above—whether the lanechange or the evading maneuver is feasible. The evaluation of thechange-over possibility computed within the scope of the reaction timeestimate can be used for this purpose.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of one ormore preferred embodiments when considered in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in detail by means of an embodiment.

FIG. 1 is a view of an extremely simplified construction of theemergency brake assistant according to the invention; and

FIG. 2 is a flow chart for determining an intervention point in timewithin the scope of an emergency brake assistant.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an emergency brake assistant NBA for automaticallydecelerating a vehicle for preventing a collision or reducing theconsequences of a collision with a detected collision object by means ofa control unit SE which receives various data u, fr and fzg and, as afunction of these data, emits a signal br for activating a brake unitnot shown here as well as, if required, emits a signal s for generatinga visual, acoustic or haptic warning. The data are, for example,environmental data that may provide information on objects and on thetype of road (for example, multi-lane). In order to be able to determinea collision object, a last-possible evading point in time and/or alast-possible braking intervention point in time for preventing acollision, additionally further vehicle data fzg, such as the currentspeed of the vehicle, the relative speed and/or the distance to adetected object are analyzed.

Finally, the driver reaction data also provide information concerningactions by the driver, particularly as to whether the driver reactscorrespondingly to a detected collision object in order to prevent thecollision.

As a function of these input data, an intervention point in time for abrake system of the vehicle will then be determined for decelerating thevehicle. At the determined intervention point in time, a signal br isemitted for activating the braking system. In addition, starting withthe detecting of the collision object, an indication signal s foractivating an acoustic, visual or haptic warning can also be triggered.

By means of the flow chart illustrated in FIG. 2, the approach fordetermining the intervention point in time within the scope of theemergency brake assistant will now be discussed in detail.

The determination operation starts in Step 10 as soon as a collisionobject was detected. In the next Step 15, events are identified from themovements of the given vehicle, as well as of the detected collisionobject to which the driver has to react for autonomously preventing thecollision. In Step 20, the last-possible points in time for a brakingtBr and an evading operation or a narrow overtaking maneuver tAusw arethen determined. The former can easily be determined by modeling asystem braking. It indicates the point in time at which at the latest afull deceleration braking has to take place in order to still preventthe collision. Several approaches exist for the determination of thelast-possible point in time for an evading or overtaking maneuver. Forexample, as explained above, a parabola can be assumed to be thetrajectory. The assumption of a circular path or an empiricaldetermination are also conceivable.

In a parallel manner, a maximal reaction time tRea is estimated based onthe momentary driving environment and as a function of the existingevent (continuous approach to the collision object driving ahead orabrupt braking of the latter or cutting-in of the collision object intothe given drive trajectory), which reaction time tRea is valid for amajority of drivers. The longer the reaction time tRea, the moreunexpected the occurrence of the event. The continuous approach to thevehicle ahead therefore causes a shorter reaction time tRea than asudden braking. Empirical tests indicate that the reaction time tRea canbe modeled as a gamma distribution. Individual parameters exist for thedifferent reaction causes, which parameters adapt the form of thedistribution. When using this gamma distribution, the percentage thatindicates the proportion of covered drivers can therefore be predefined.When the predefinition amounts to 80%, only 20% of drivers remain whosereaction time tRea in the tests is still longer than the resultingvalue.

In addition, the reaction time tRea is increased by the number ofconceivable action alternatives. Thus, if the driver can decide betweenbraking and overtaking (he therefore has 2 alternatives), his reactiontime tRea will logarithmically increase according to Hick's Law. Fromthe system perspective, this means that the possibility of carrying outan overtaking or evading maneuver has to be examined. For this purpose,the distance as well as the relative speed with respect to the vehicleahead in the adjacent lane, the clearance adjacent to the given vehicleas well as the relative speed and the distance of a vehicle approachingfrom the rear in the adjacent lane are analyzed in a three-step process.If all three checks do not point to any danger in the adjacent lane,there is the possibility of a lane change—the reaction time tRea isextended. The modeled reaction time tRea will start running with theoccurrence of an event.

A preliminary intervention point in time tEing_v (under certaincircumstances, also already the final intervention point in time tEing)is determined from the modeled reaction time tRea and the currentsituation during the next steps. For this purpose, it is checkedbeforehand in Step 30 whether, with respect to time, the last-possiblebraking point in time tBr is already occurring before the last-possibleevading point in time. If this is not so, the last-possible brakingpoint in time tBr will be defined in Step 35 as the final interventionpoint in time tEing. The process will then be terminated immediately.

However, if the last-possible braking point in time tBr already occursbefore the last possible evading point in time tAusw, a preliminaryintervention point in time tEing_v will be determined in the next Step40. In this case, the driver reaction plays no role at first. Only theend of the reaction time tRea—thus the current TTC (time-to-collision)minus the (remaining) reaction time—will be analyzed. This results inthree different cases:

Case 1: The reaction time tRea ends before the last-possible brakingpoint in time tBr. Here, the intervention should take place at thelast-possible braking point in time tBr.

Case 2: The reaction time tRea ends between the last possible brakingpoint in time tBr and the last possible evading or overtaking point intime tAusw. Here, the intervention is to take place at the last-possiblebraking point in time tBr if a lane change is not possible, and at theend of the reaction time tRea, if a lane change is possible.

Case 3: The reaction time tRea ends after the last-possible overtakingpoint in time tAusw. In this case, the driver can no longer reactautonomously to the impending collision. The intervention takes place atthe last-possible braking point in time tBr. If the latter has alreadybeen passed, the intervention will take place immediately.

In the subsequent Step 50, the driver's reaction fr to the event isevaluated within a predefined time period dt (during and after the endof the reaction time tRea). As reactions fr, a differentiation is madebetween an overtaking maneuver and a braking. A decreasing overlap ofthe given vehicle with the vehicle driving ahead or a high accelerationmay indicate an overtaking maneuver. The operation of the brake pedal ora release of the accelerator pedal may indicate a braking.

However, the reaction fr alone is not sufficient for changing thepreliminary intervention point in time tEing_v determined in thepreceding step. For this purpose, an additional checking is necessary asto whether the evading or overtaking maneuver is actually feasible orwhether the applied deceleration is actually sufficient for preventingthe collision. If this is so (Step 60), it is assumed that the driver isautonomously alleviated the situation. The final intervention point intime tEing is therefore delayed to the last-possible evading point intime (tAusw delayed). Although here the collision is no longeravoidable—because of the recognized adequate reaction, this point intime should not be reached at all. In the event of a false reactionrecognition, the full deceleration will still reduce the consequences ofthe collision. If the reaction fr is not feasible/sufficient or noreaction fr can be recognized (Step 55), the preliminary interventionpoint in time tEing_v will become the final intervention point in timetEing. The process ends in Step 70.

By including the driver reaction in the determination of theintervention point in time for a danger braking system, the number offalse activations in the case of high relative speeds can be drasticallyreduced. If the driver exhibits no or an inadequate reaction, thecollision is avoided by the danger braking system. In contrast, if thedriver reacts sufficiently to the event, an intervention does not takeplace before a point in time at which an overtaking or evading can alsono longer take place.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

1. An emergency brake assistant for automatically decelerating a vehicleto prevent a collision or reduce the consequences of a collision with adetected collision object, at a determined intervention point in time,wherein a brake system of the vehicle is automatically activated suchthat a collision with the detected collision object can be prevented orconsequences of the collision can be reduced, wherein the interventionpoint in time is determined as a function of a determined end point intime of a driver reaction time and of a determined last-possible brakingpoint in time.
 2. The emergency brake assistant according to claim 1,wherein the determined intervention point in time is further determinedbased on a determined last-possible evading point in time.
 3. Theemergency brake assistant according to claim 1, wherein the determinedintervention point in time is determined such that, at the determinedend point in time of the driver reaction time, which occurs before thedetermined last-possible braking point in time, the last possiblebraking point in time is defined as a preliminary intervention point intime, or that, at the determined end point in time of the driverreaction time, which occurs before the determined last-possible evadingpoint in time and after the determined last-possible braking point intime, the last-possible braking point in time or the determined endpoint in time of the driver reaction time is defined as the preliminaryintervention point in time, or that, at a determined last-possibleevading point in time, which occurs after the determined last-possiblebraking point in time and before the determined end point in time of thedriver reaction time, the last possible braking point in time is definedas the preliminary intervention point in time.
 4. The emergency brakeassistant according to claim 2, wherein the determined interventionpoint in time is determined such that, at the determined end point intime of the driver reaction time, which occurs before the determinedlast-possible braking point in time, the last possible braking point intime is defined as a preliminary intervention point in time, or that, atthe determined end point in time of the driver reaction time, whichoccurs before the determined last-possible evading point in time andafter the determined last-possible braking point in time, thelast-possible braking point in time or the determined end point in timeof the driver reaction time is defined as the preliminary interventionpoint in time, or that, at a determined last-possible evading point intime, which occurs after the determined last-possible braking point intime and before the determined end point in time of the driver reactiontime, the last possible braking point in time is defined as thepreliminary intervention point in time.
 5. The emergency brake assistantaccording to claim 3, wherein at the determined end point in time of thedriver reaction time, which occurs before the determined last-possibleevading point in time and after the determined last-possible brakingpoint in time, the last-possible braking point in time is defined as thepreliminary intervention point in time if an evading maneuver is notfeasible, and the determined end point in time of the driver reactiontime is defined as the preliminary intervention point in time, if anevading maneuver is feasible.
 6. The emergency brake assistant accordingto claim 4, wherein at the determined end point in time of the driverreaction time, which occurs before the determined last-possible evadingpoint in time and after the determined last-possible braking point intime, the last-possible braking point in time is defined as thepreliminary intervention point in time if an evading maneuver is notfeasible, and the determined end point in time of the driver reactiontime is defined as the preliminary intervention point in time, if anevading maneuver is feasible.
 7. The emergency brake assistant accordingto claim 3, wherein the intervention point in time can only bedetermined in such a manner if the last-possible evading point in time,with respect to time, is after the last-possible braking point in time.8. The emergency brake assistant according to claim 4, wherein theintervention point in time can only be determined in such a manner ifthe last-possible evading point in time, with respect to time, is afterthe last-possible braking point in time.
 9. The emergency brakeassistant according to claim 5, wherein the intervention point in timecan only be determined in such a manner if the last-possible evadingpoint in time, with respect to time, is after the last-possible brakingpoint in time.
 10. The emergency brake assistant according to claim 6,wherein the intervention point in time can only be determined in such amanner if the last-possible evading point in time, with respect to time,is after the last-possible braking point in time.
 11. The emergencybrake assistant according to claim 1, wherein when determining theintervention point in time, the driver reaction, during at least one ofthe determined driver reaction time and after the end point in time ofthe determined driver reaction time, can be taken into account.
 12. Theemergency brake assistant according to claim 3, wherein when determiningthe intervention point in time, the driver reaction, during at least oneof the determined driver reaction time and after the end point in timeof the determined driver reaction time, can be taken into account. 13.The emergency brake assistant according to claim 1, wherein theintervention point in time can be determined such that the determinedlast-possible evading point in time is defined as the intervention pointin time when an evading operation to be carried out by the driver isrecognized or assumed and a feasibility of the evading maneuver isrecognized.
 14. The emergency brake assistant according to claim 3,wherein the intervention point in time can be determined such that thedetermined preliminary intervention point in time is defined as theintervention point in time when an evading operation to be carried outby the driver is not recognized or not assumed.
 15. The emergency brakeassistant according to claim 1, the driver reaction time can bedetermined as a function of the occurrence of the collision objectand/or of the number of the conceivable action alternatives when acollision object is detected.
 16. A method for automaticallydecelerating a vehicle comprising: determining a intervention point intime based on a determined end point in time of a driver reaction time,a determined last-possible braking point in time, and a determinedlast-possible evading point in time; and activating, automatically, abrake system of the vehicle at the determined intervention point in timesuch that a collision with a detected collision object is prevented orconsequences of the collision reduced.
 17. The method according to claim16, wherein the intervention point in time can be determined such thatthe determined last-possible evading point in time is defined as theintervention point in time when an evading operation to be carried outby the driver is recognized or assumed and a feasibility of the evadingmaneuver is recognized.
 18. The method according to claim 16, the driverreaction time can be determined as a function of the occurrence of thecollision object and/or of the number of the conceivable actionalternatives when a collision object is detected.